If the pixel pitch and read noise per pixel are both halved, there will be no change in noise at all. So, if a 32 MP mFT sensor had pixels with 71% the read noise of a 16 MP sensor, then there would be no difference in noise.

Halving the pixel pitch would not halve the read noise.

I made no such claim. I simply said that if that were the case, then there would be no noise penalty for smaller pixels.

Were that the case, all modern digital cameras would have much finer pixel pitches than they currently do.

Funny thing about that. We all know that they can make really small pixels that are very good quality -- just look at the Sony RX100. An mFT sensor with RX100 pixels would have 40 MP, and a FF sensor with the same pixels would have 150 MP. So, why don't they? The tech is already here. Why is 20 MP good for the RX100, but 40 MP of the same pixels is not good for mFT and 150 MP of the same pixels is not good for FF?

That's a discussion worth having, methinks.

Have you really looked at the sharpness of the RX100 shots? Even the macros are somewhat soft, not bad just soft and with seemingly less detail...

The question is how they would compare if the sensor had, say, 12 MP instead.